One of the steps required to install Oracle on Linux is to Install all the Linux packages, rpm's, needed by Oracle, and their dependencies. That is followed by creating the Oracle user account and groups and setup the parameters for the kernel.
All of these tasks can be automatized by installing a single rpm that is distributed by Oracle, the Oracle-Validated rpm.
On the Oracle Enterprise Linux 5.5 distribution disk it is included the Oracle-Validated rpm and also the ASMLib related rpms.
The rpm can be installed as part of the Linux install process, as explained on Sergio Leunissen post from 2009
Another option, if you have your server connected to the Internet, is to run the install using Yum; it will install the oracle-validated rpm and download all required dependencies.
Yet another option, if you don't have access to the Internet, is to setup a local or NFS mounted repository that contains all rpm's included on the Linux distribution disk.
In this post I'm including an example of the steps required to setup a local rpm repository and install the Oracle-Validated rpm and it's dependencies from it: